2005 Annual Report
City of Fort Collins
Mosquito Control Program
October 2005
Colorado Mosquito Control, Inc.
695 North 7th Ave. Brighton, Colorado 80601
(303) 558-8730 Fax 558-8734
E-Mail: [email protected]
CMC Website: www.comosquitocontrol.com
ON THE COVER:
THIS IS YOUR BRAIN WITH WEST NILE VIRUS…..
BRAIN SCAN FALSE COLOR IMAGE OF INCREASED (RED) AND REDUCED (BLUE/GREEN) BRAIN
ACTIVITY AND BLOOD FLOW IN A PERSON 2 YEARS AFTER INFECTION WITH WEST NILE VIRUS.
BITTEN BY AN INFECTED MOSQUITO IN JULY OF 2003 ON THE COLORADO FRONT RANGE, THIS
PERSON WENT FROM A NORMAL, HEALTHY AND ACTIVE ADULT TO BEING UNABLE TO
UNDERSTAND AND COMMUNICATE WITH FRIENDS AND FAMILY AND SUFFERED NUMEROUS OTHER
SEVERE PHYSICAL AND MENTAL SYMPTOMS. AND NOW TWO YEARS LATER, STILL SUFFERS FROM
SIGNIFICANT MEMORY PROBLEMS, SEVERELY REDUCED COGNITIVE STAMINA, FATIGUE,
DIFFICULTY IN CONCENTRATING, AND HEADACHES.
DURING THE SUMMER OF 2003, THE STATE OF COLORADO EXPERIENCED THE WORST EPIDEMIC OF
HUMAN MOSQUITO-BORNE DISEASE ON RECORD IN THE WESTERN UNITED STATES WITH NEARLY
3,000 CASES AND 63 DEATHS. IN 2004 NEARLY 300 CASES AND 3 DEATHS WERE RECORDED.
AS OF OCTOBER 12, 2005 THE RISK OF WNV INFECTION IN COLORADO CONTINUES. 83 HUMAN CASES
OF WEST NILE VIRUS HAVE BEEN REPORTED IN COLORADO WITH ONE DEATH, IN MORGAN COUNTY.
______________________________________________________________________________
THE MOSQUITO LIFE CYCLE
City of Fort Collins
Mosquito Control Program
2005 Annual Report
1. Introduction........................................................................................ 2
2. 2005 Season Summary ..................................................................... 3
3. Mosquito Control Staff ..................................................................... 5
4. Customer Calls .................................................................................. 5
5. Larval Mosquito Control .................................................................. 6
6. Adult Mosquito Control ................................................................. 11
7. Virus Surveillance Program.......................................................... 13
8. Public Education ............................................................................ 14
9. Mosquito Research ........................................................................ 15
10. APPENDIX (Maps & Figures).................................................... 16
1. Introduction
A. Background
The City of Fort Collins Mosquito Management Program has completed its 2nd
year of cost effective bio-rational integrated mosquito control, and its 3rd year of
mosquito surveillance. By contracting with Colorado Mosquito Control, Inc. (CMC) the
City has 1) reduced the number of disease-vectoring mosquitoes, most before they can
arise from the water to spread disease; 2) provided all residents with effective mosquito
control using trained technicians who are able to concentrate on constantly changing
mosquito populations; 3) freed up municipal personnel to perform their regular duties;
and 4) provided a cost savings to the City.
B. Program Goals
Integrated Pest Management:
“A process consisting of the balanced use of cultural, biological, and least-toxic
chemical procedures that are environmentally compatible and economically feasible
to reduce human disease to a minimal level.”
The goal of Colorado Mosquito Control, Inc. (CMC) is to provide all residents of
the City of Fort Collins with the best in safe, effective, modern integrated mosquito
management. This environmentally friendly program always uses cultural and biological
control choices first, such as naturally occurring bacteria. These efforts are all designed
to reduce target mosquito populations to below established disease thresholds.
The Mosquito Control Area now contains approximately 112.8 square miles, 61.7
square miles of which are outside City limits (See Figure 1 for a map of the City’s
Program). Although many of the mosquito production sites are outside the City limits, all
are well within the flight range of most mosquitoes. Larval control work outside the City
will continue to remain a critical part of the overall operation of CMC.
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2. 2005 Season Summary
All aspects of the mosquito program attempt to minimize the number of WNV
human cases in Fort Collins. Most importantly, all Fort Collins field staff were
immediately trained to recognize the larvae of Culex mosquitoes, the type responsible for
transmitting WNV. Second, these Culex production sites were always given first
priority.
The season in summary:
● There were 10 human cases of West Nile Virus (WNV), 2 of which were
serious, in Fort Collins in 2005. There were also 10 WNV-positive mosquito
samples, 12 WNV-positive birds, and 1 WNV-positive squirrel. Compare this to
2004 with 10 human cases, 2 positive mosquito samples, and no positive birds.
The data over the last 4 years strongly indicates that WNV is likely to be present
in varying amounts for years to come. (See Figure 1 for the locations of WNVpositive mosquitoes in Fort Collins).
● The larval control area was roughly the same size as in 2004 (112 sq.
miles), with some reductions in size because the Town of Timnath took over a
small section, and because the outer areas were eliminated at the end of July
due to workforce issues. (See Figure 1).
● The summer in 2005 had nearly the same amount as rain as the
epidemic 2003 year, but was slightly cooler. This resulted in WNV starting its
peak later, with fewer human cases. (See Figure 2).
● Because the City did not adulticide in 2005, the total number of calls
plummeted. Most of the remaining calls were to report standing water. (See
Figure 3).
● 88% of the treatments were made with environmentally friendly bacterial
products, showing a decrease in both larviciding oil and insect growth regulators
(See Figure 4).
● Field staff found a record number of mosquito sites in 2005 – an
increase of 497 sites to 1,364 sites by the end of 2005. (See Figure 5)
● Improved Quality Control methods revealed that over 70% of larval
inspections were done accurately, and resulted in immediate retraining efforts for
the remaining 30% of inspections that needed improvement.
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● The number of adult mosquitoes increase slightly compared to last year,
but the data strongly suggest that the larval program has been highly effective in
reducing the number of Culex mosquitoes – the type that carries WNV. (See
Figures 6, 7, 8, 9, 10, and 11).
● CMC started 3 innovative methods of larval control in 2005 – staging a
one day “Fish Giveaway” for local residents to stock their backyard ponds with
mosquito-eating fish, stocking agricultural ponds throughout the summer with the
same type of fish, and treating Culex-producing trash cans at all City parks and
schools.
Many have asked what the future of WNV will be like here in Fort Collins. After
4 consecutive years with virus activity, it is highly probable that WNV is here to stay.
John Pape, an epidemiologist at the Colorado Department of Health and Environment,
was quoted at the end of last year, “2003 was likely as bad as it gets, 2004 is likely as
good as it gets, every year from now on will be somewhere in between.” His words have
rung true.
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3. Mosquito Control Staff
The 2005 Fort Collins mosquito staff
consisted of 17 Full-time Equivalent employees
(FTE). Specifically, we had 1 Manager, 1 Field
Supervisor, 9.25 Field Technicians, 0.25 Fish
Program Manager, 1.5 Urban Programs
Technicians (i.e., for Backyard Program, Storm
Drain Program, and Public Education Program),
0.5 Surveillance Supervisor, 1 Surveillance
Technician, 0.5 Maintenance Technician, 0.5
Quality Control Supervisor, and 1.5 Office Staff.
In 2004 we had 17.5 FTEs.
4. Customer Calls
There was no fogging sponsored by the City of Fort Collins in 2005, which likely
caused the 85% drop in calls to the mosquito office. Most of the 2005 calls were to
citizen reports of standing water.
The number of total customer calls to the mosquito office in 2005 was 151. Of
these, 65 were to report potential mosquito breeding sites, 39 were to request WNV or
other information, 20 were biting mosquito complaint calls, 13 were miscellaneous calls,
4 were to request inclusion on the fogging notification or shutoff lists, 2 were to report
dead birds for WNV testing, 2 were to request mosquitofish, 3 were to request special
event spraying, 1 was a complaint about allergies, and 1 was a complaint about bees.
Compare this to 2004 (998) and 2003 (423). (See Figure 3).
The complaint calls discussed above are used as a secondary indicator of where
populations of adult mosquitoes are high. The primary indicator is our series of adult
mosquito light traps located in all sections of the City. We use traps as the primary
indicator because tolerance to mosquitoes, and desire to report high numbers, varies
greatly from person to person. Setting adult mosquito traps allows us to quickly identify
a problem area before residents have had several days to build up concerns about a spike
in mosquito populations.
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5. Larval Mosquito Control
Weather conditions were nearly ideal for mosquito production in 2005, but CMC
staff kept total populations, and especially Culex mosquitoes, very low. This was done
through increasing the number of sites by 36% and by targeting high production sites
using a “site priority” system. (See Figure 5).
Because of WNV, emphasis was always put on finding and treating sites that
contained Culex mosquito larvae. (Culex mosquitoes are the primary transmitters of
WNV in Colorado). When time was short, this sometimes meant allowing nuisance
mosquitoes to escape while time and manpower was spent treating potential disease
producing larvae. Fortunately, since all field staff were trained to identify Culex
mosquitoes by eye while sampling, it was quite simple to determine which sites
contained Culex mosquitoes.
“Larviciding” is the process of inspecting, and if necessary, treating, any standing
water for mosquitoes while they are growing under water. Currently, CMC checks
every potential larval development site (e.g., ponds,
wetlands, agricultural fields, residential backyards) in the
Fort Collins area (now 1,472 sites) based on its
production history. Therefore, the highest producing
sites were checked more than once per week, and the
lowest producing sites checked once or twice once per
month. Some sites were checked when an irrigation
event was expected and/or a large rainstorm had just
occurred.
The sites were reached on foot or by using an All
Terrain Vehicle (ATV). Use of the ATV is critical in the
large and/or hard to reach areas. The ATV allowed the
field staff to cover large sites quickly and efficiently.
The staff checked for larvae at each site by taking water
samples with a plastic dipper. If larvae were present, the
site was treated with one of the products described below.
The product most commonly used in 2005 was a virtually non-toxic substance
derived from a bacterium called Bacillus thuringiensis sub. israelensis (Bti). The active
ingredient is used in a form marketed as “Vectobac”. Byproducts from Bti kill mosquito
larvae within approximately 24 hours of application, and require additional treatments
every 4-7 days as long as larvae are present
A second bacterium, Bacillus sphaericus (H-5a5b), referred to as “Bs,” is a
classical biological control organism. Bs was used throughout the season in a form
marketed as “Vectolex”. Bs kills mosquito larvae within approximately 48 hours, and
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has a longer period of effectiveness (approximately 21 days). It is effective longer
because the Bs bacteria have the ability to reproduce in the cadavers of dead larvae.
In some cases an extremely thin larviciding oil must be used. The larviciding oil
used in 2005 is marketed as “Bonide Larviciding Oil.” It consists of mineral oil with a
small percentage of spreading agents. It is normally used only where mosquitoes
developed to the late larval or pupal stage, or if larval populations were so high that Bti
would not be effective. The oil was used quite a bit less in the 2005 season because the
staff were able to visit the sites more quickly, thus catching most mosquitoes in the
larval stage.
We also use a mosquito growth inhibitor called Methoprene in select locations. It
is marketed in several forms under the trade name of “Altosid." Altosid products work
by preventing larval mosquitoes from developing into adults. Altosid has no noticeable
effect on most other animals, and allows the larval mosquitoes to grow normally until
the pupal stage. This allows them to play their normal role in the ecosystem -- as a food
source for fish and other aquatic organisms. It has several limitations, so can only be
used in a few areas.
In 2005, 842.8 acres were treated with the bacteria Bti, 136.8 acres with the
bacteria Bs, 97.4 acres with larviciding oils, and 32.8 acres with the mosquito growth
regulator Methoprene. See Figure 4 to compares the use of these products over the past
few years. Note that in 2003, all 500 acres were treated over 2 days by helicopter. In
2004 and 2005, several thousand treatments were done on foot or on ATV.
The following is a summary of larviciding efforts in 2005:
1) WNV Targeting - CMC field staff were again trained to identify Culex larvae,
enabling them to concentrate on sites that often produce these mosquitoes. In total, they
killed approximately 2.4 Billion Culex larvae (the species that transmit WNV), and 5.3
billion larvae overall.
2) Products Used – In 2005, approximately 76% of the acreage was treated with
Vectobac products, 12% with Vectolex products, 9% with larviciding oil, and 3% with
Altosid products. See Figure 4 for a comparison with the last few years.
3) Site Inspections - The staff made 8,211 visits to mosquito larvae sites,
compared to 9,680 in 2004 and 0 in 2003. This was 15% lower than last year because
we were able to use 2004 data to increase visits to sites that produce heavily, and reduce
visits to sites that do not.
3) Size of Control Area -The larval surveillance area in 2005 was 112.8 square
miles through July, and cut to approximately 15 square miles for the remainder of the
season. This reduction was due to a decrease in field staff.
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4) Number of Larval Sites -The total number of larval sites has been increasing
dramatically since the start of the program – from 70 sites in 2003 (a one time
treatment attempting to stem rampant WNV transmission) to 867 in 2004 to 1,364
by the end of 2005. There would be more sites, but we inactivated 52 sites due to lack
of production and deleted 56 sites because they were either destroyed or the water
source was removed (e.g., irrigated farm land sold for development). (See Figure 5)
5) Number of Treated Acres -The number of acres treated in 2005 was 1,110.7.
In 2004 the treated acreage was 1,256.9. This was less than last year, likely because less
rain in 2005 resulted in smaller acreage per site. Note that the total number of larvae
killed was higher in 2005, despite lower total acreage treated.
6) Inspection Efficiency – It is impossible to know if a given mosquito site will
or will not be producing larvae on a given day unless it is physically inspected by a
technician. However, using historical data, CMC can prioritize which sites should be
checked semi-weekly, weekly, or less often. This year, approximately 83% of sites
were wet when inspected, and 34% were producing larvae when inspected. In 2004,
these numbers were 78% and 21%, respectively. This huge increase in efficiency was
due to CMC’s unique site priority system.
7) Helicopter Usage – Helicopters were not used this year because CMC
employed an additional one and a half “attack team” field technicians who assisted with
the chronically large mosquito sites. However, a helicopter may become necessary in
the future if mosquito populations temporarily expand beyond our “on the ground”
employee capabilities.
8) Storm Drain Program - The storm drain program is now in its 2nd year, and
we now have enough data to streamline it for following years.
CMC staff monitored 3,353 individual storm drains (often called catch basins)
throughout the City. There were 4,924 visits to these drains. During 458 of these visits,
the technician manually sampled the drain for mosquito larvae (the remainder were only
visually inspected, and treated if there was water collecting in the drain at the time of the
visit). The 4,924 visits resulted in 698 treatments – 636 with Altosid 30 day briquettes,
21 with Altosid 30 day pellets, and 41 with larviciding oil.
The primary species found in storm drains was Culex pipiens, a known vector of
WNV. Culex tarsalis, also a WNV vector, was also found in a few drains.
9) Residential Backyard Program –Culex pipiens is a known vector of WNV,
and it usually is found primarily in residential settings. In 2004 we standardized an
inspection system to keep on top of residential properties which produce Culex
mosquitoes. In 2005, this program expanded from 41 yards to 121, resulting in
significant reductions in Culex pipiens, and numerous opportunities to educate
homeowners. These contacts with homeowners resulted in 9 backyard sites being
cleaned up by the owner, therefore eliminating any “breeding” potential.
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10) Fish Program - In the summer of 2005, Colorado Mosquito Control
implemented a new fish program that will aid in the biological control of mosquitoes.
The species of choice was the “fathead minnow” (Pimephales promelas). This species
was chosen because of several qualities this small fish possesses: 1) They are endemic to
Colorado, specifically to the Platte, Republican, Arkansas, and Rio Grande basins; 2)
They are excellent consumers of mosquito larvae: and 3) They are very tolerant in harsh
conditions. These minnows have a life span of approximately three years and are
prolific spawners with the ability to establish viable populations throughout the state.
Colorado Division of Wildlife approves and recommends the use of Fathead minnow for
our purposes. Species such as the “mosquitofish” (Gambusia affinis) are not
recommended because they are not native and can easily displace native species in
Colorado.
Both agricultural and residential ponds were targeted. For residential ponds,
CMC sponsored a “Fish Giveaway” on a Saturday in mid-summer at the Downtown Ace
Hardware. More than 1,700 fish were given to residents to stock approximately 50
ornamental ponds in the Fort Collins area. From both mosquito control and public
awareness perspectives, it was a huge success.
For agricultural mosquitoes, 15 ponds in the Fort Collins area were evaluated by
CMC for stocking. Of these, 7 ponds were stocked with fathead minnows at the rate of
400-600 fish per acre surface area, using approximately 1,520 fish total. When CMC
evaluated each stocked pond at the end of the season, 1 pond definitely still had a viable
fish population, 4 still had good conditions for fish survival (although no fish were seen
during the brief visit), and 2 ponds had dried up. In summary, 1 stocking was definitely
successful (and will likely not need restocking next year), 4 were likely successful (and
may not need to be restocked next year), and 2 will likely need to be restocked next year.
11) Quality Control Program – In 2005 the quality control program was
formalized. It had two parts – a half-time Quality Control Supervisor who randomly
chose sites to inspect, and quizzes several times a week throughout the season. The
random inspections resulted in huge improvements in identification of training needs,
product usage, acreage estimation, and various other larval control issues. The quizzes,
which were often based on training deficiencies discovered in the field, reinforced
appropriate treatment strategies for the experienced employees, and retrained the new
employees.
The Quality Control Supervisor found that approximately 70% of the 8,211 site
visits were completed accurately and efficiently. Improvements were needed on 30% of
the visits, such as the technician using too little or too much larvicide per acre, missing
part of a site, returning too late, under or overestimating acreage, taking too much or not
enough time, etc. Most of these deficiencies resulted in immediate retraining of the
technician by the Field Supervisor and/or the Quality Control Supervisor. Most issues,
once identified, were quickly rectified.
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12) Park and School Cans – Because of an unexplained increase in Culex
pipiens late in the summer, CMC decided to investigate if trash cans in parks and schools
could be a potential source of this species. On August 31 and September 1, CMC staff
inspected all cans at 23 schools, 1 park, the Colorado State University Campus, and the
Archery Range. Please note that these inspections were done just after schools came
back into session. Therefore, it was less likely to find larvae at this time because many
schools began regularly emptying cans in the last weeks of August.
In total, 223 cans were inspected by CMC for Culex pipiens larvae. (i.e., 5 cans
from Westfield Park, 30 from the CSU campus, 5 from the Archery Range, and 183 from
various schools. At the schools, 21 cans (11%) were producing. At CSU, 4 cans (13%)
were producing. At the Archery Range, 2 cans (40%) were producing. Of all producing
cans, there was an average of 32 larvae per dip. This equals approximately 1,760 larvae
per can. In other words, approximately 40,480 Culex mosquitoes were killed by CMC in
this one round of inspections. At this point it appears that trash cans pose a higher
WNV risk than storm drains. Therefore, CMC recommends that periodic trash can
inspections get higher priority than storm drain inspections in future larviciding
programs in Fort Collins.
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6. Adult Mosquito Control
A. Monitoring of Adult Mosquitoes
Surveillance of adult mosquitoes in Fort Collins centered on locating from where
Culex mosquitoes arise. Nuisance mosquitoes were noted and attempts were also made
to locate the water sources from which they
were arising, but most efforts went towards
Culex mosquitoes.
In 2005, mosquito populations in the City
were monitored at 45 adult light trap locations
(approximately 1 per square mile). This is an
increase of 1 trap location compared to 2004.
Battery-operated “light traps” were set weekly
in each location, and gravid traps were set every
3 to 4 weeks in each location. A few traps a
week were also placed in the yards of residents
who complained of excessive mosquitoes.
Results of the monitoring efforts are
shown in Figures 6 through 11. Note in
Figures 7 through 10 that mosquito populations
were a mere shadow of what they were in 2003
(Figure 11 shows nuisance floodwater
mosquitoes, which were intentionally not
treated at various times throughout the season).
The data in Figure 9 strongly suggest that
the notable reduction in Culex mosquitoes is
due to the presence of a larval control
program in Fort Collins. Specifically, Culex
tarsalis populations were much higher in 2003
when Loveland had a mosquito program and
Fort Collins did not. In the following 2 years,
the Culex tarsalis populations have been nearly
identical. The only significant difference
between the two Cities was the presence or
absence of a mosquito program. A similar trend
is seen is Culex pipiens, not shown.
Figure 6 displays the general trend in
mosquito populations over the last 3 years.
Figure 7 displays weekly changes in mosquito populations within each year.
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Some species of mosquitoes can transmit West Nile Virus, Western Equine
Encephalitis and St. Louis Encephalitis and others cannot. Therefore, it is critical to
know what species are present in Fort Collins, where they are, and when they are there.
Figure 8 shows the relative abundance of these and other species in the Fort Collins/Ft.
Collins area. The samples were
taken within, or immediately
adjacent to, City limits.
Figure 8 represents two
important items: 1) the changing
overall populations from year to
year, and 2) the changing
proportions of one species over
another. First, note the population
of “floodwater” (i.e., nuisance)
mosquitoes, as indicated by blue
tones. Second, note the Culex
mosquitoes, as indicated by the red
tones. These Culex mosquitoes
have been noticeably suppressed.
B. Adult Mosquito Control
The primary emphasis of the Fort Collins program is to control mosquitoes in the
larval stage, using safe biological control products. However, CMC was prepared to
adulticide if disease conditions made it absolutely necessary. Fortunately, WNV was not
present over a large area, so no adulticiding was requested by City officials.
It is important to note that CMC did adulticide on numerous occasions within the
City of Fort Collins in 2005 at the request of several private homeowners’ associations.
It is also likely that adulticiding was done by other mosquito control contractors within
City limits.
C. Resident Notification
Although no adulticiding was planned by the City of Fort Collins, at least four residents
requested to be placed on a “no spray” list. Their information was taken by CMC office
staff for future reference.
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7. Virus Surveillance Program
West Nile Virus has not behaved like other mosquito-borne diseases in Colorado.
Unlike Western Equine Encephalitis and St. Louis Encephalitis, which appear at low
levels every 7 to 10 years, WNV looks like it will be present every year at widely varying
levels.
The purpose of a surveillance program is to be an early warning system. In other
words, the system is intended to alert mosquito personnel of an impending health crisis.
The key is that the system gives enough advance warning that mosquito control personnel
can take effective steps to minimize the number of human cases.
As in 2004, all Culex mosquitoes were sent to either the Centers for Disease
Control (CDC) or the State Health Department for WNV testing. Sending this
exceptionally large numbers of Culex mosquitoes for testing is highly unusual in
Colorado. Most parts of
the state have only 2 traps
per county. There are over
80 traps within Fort
Collins and Loveland
alone. We are fortunate
because the CDC has been
conducting a multi-year
WNV study within the two
Cities. CDC’s study
depends on consistent
collections in both cities
for the next several
years.
There were 10
mosquito samples found
positive for WNV in Fort
Collins 2005. See Figure
1 for details about the locations and dates of the positive mosquitoes. In 2004 there were
2, and in 2003 there were over 50.
There were 10 humans found positive for WNV for people with Fort Collins
addresses in 2005. Compare this to 10 in 2004 and 302 in 2003.
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8. Public Education
CMC normally does a great deal of public education through hundreds of personal
contacts in the field and through hundreds of calls to our office. However, in 2005 we
hired a part-time employee to both take some of the residential workload off of the field
technicians and to attend public functions.
To this end, the “Backyard Technician” attended 7 city-sponsored public events,
such as concerts, farmer’s markets, etc. to give out information about the City’s mosquito
control program, WNV, and mosquito control. In addition, she helped organize the first
annual “Fish Giveaway” where over 50 City residents received information, and of
course, fish. (See item #10 in the Larval Mosquito Control section above for details).
An additional part of this job was investigating calls from the public regarding
potential mosquito sites. This resulted in her locating 80 new backyard ornamental ponds
that were producing mosquitoes, not to mention dozens of productive conversations with
homeowners.
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9. Mosquito Research
CMC seeks to assist in mosquito research that will improve the quality and
efficiency of our mosquito control programs.
In 2005, we were involved with the following research programs:
1) Centers for Disease Control West Nile Virus Study: Throughout the
Cities of Loveland and Fort Collins, CMC collected and identified adult mosquitoes
weekly from mid-May to mid-September using CO2-baited light traps. These
mosquitoes were identified to species , then sent to the Centers for Disease Control in
Fort Collins for testing for West Nile Virus. CMC, the Larimer County Health
Department, and the Colorado Department of Public Health and Environment used this
information for immediate operational decisions. This information will also be used by
the Centers of Disease Control to make mosquito control recommendations to
communities across the country.
2) Permethrin Resistance Study: Mike Doyle of CMC is serving on the
committee of Adam Strong, a Naval Medical Entomologist presently earning his M.S.
degree at Colorado State University. In summary, Petty Officer Strong is trying to
determine if: 1) adult mosquitoes are becoming resistant to permethrin, a botanically
based chemical commonly used in residential, agricultural, and mosquito control
pesticides. (Currently, permethrin is the primary ingredient in CMC’s mosquito
adulticides), and 2) If the source of resistance is more closely tied to agricultural,
residential, or mosquito control sources of permethrin.
Specifically, Petty Officer Strong is working on a research project to determine
the level of resistance the major West Nile virus-transmitting mosquito, Culex tarsalis,
has to permethrin. During the first stage of the project, he reared a lab strain of Culex
tarsalis and conducted standard CDC bottle and bioassays using a permethrin containing
insecticide called “Aqua-Reslin RTU”. Aqua-Reslin RTU is the primary adulticide used
by CMC. These experiments determined baseline levels of resistance and enzyme levels
to which the field strain are compared. Over the summer of 2005, he worked with CMC
Inc. and collected Culex tarsalis as larvae from several CMC Inc. treatment sites in
northern Colorado. These larvae were reared to adulthood and then tested for resistance
to permethrin using bottle and bioassays by comparing the results to the baseline lab data.
After analyzing the preliminary data, it appears that the field Culex tarsalis strain exhibits
some resistance to permethrin. The summer of 2005 resulted in an identification of
reliable Culex tarsalis collection sites, fine-tuning of rearing methods, and determining a
discriminating insecticide dose to use in the bottle assays. During the summer of 2006,
many more collections and experiments will be run and analyzed. Using SAS statistical
analysis, data will be compared to determine if there are any significant differences in
resistance between the lab and field strains, different treatment sites, and the same
treatment sites over time. Possible mechanisms behind that resistance will be analyzed
and tied to the different strains of mosquitoes, location of larval sites, and times of larvae
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collections. For example, is the resistance related to residential, agricultural, mosquito
control, or other sources of permethrin in the environment? Is the resistance due to
exposure to permethrin or to some other closely related chemical compounds? This study
will help CMC Inc. in managing mosquito populations in northern Colorado by applying
local resistance data to adulticide-related decisions.
3) USDA National Wildlife Research Center WNV Study – CMC is
providing adult mosquito surveillance data to researchers with the Wildlife Disease
Program at the USDA National Wildlife Research Center. They are trying to use the
swallows as a predictor of when and where WNV will affect the human population. If
they can detect an emerging problem in a localized area, perhaps a city/county can begin
a more intensive mosquito control effort in that area. The questions they want to answer
are:
1) Is there a difference in WNV activity in swallows between areas where mosquito
control was performed and not performed? and 2) Can WNV activity in mosquitoes and
WNV activity in swallows be matched in a particular area? This study is planned for the
next 3 years, so relies on the City of Fort Collins continuing their mosquito surveillance
program.
10. APPENDIX (Maps & Figures)
Please see following pages.
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Figure 1
City of Fort Collins Mosquito Program
2005
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S
#
#
S
S
#
S
#
S#
#
S#
S
Legend
S
#
S
#
Positive_wnv_mosq_2005.shp
Timnath_larval_area_2005.shp
Climits.shp
Loveland_limits.shp
Fc_larval_control_area_2005.shp
Lv_larval_control_area_2005.shp
S
#
Hoa_larval_routes_2005.shp
S
#
Figure 2
65.5
9.0
65.0
8.0
64.5
7.0
64.0
6.0
63.5
5.0
63.0
4.0
62.5
3.0
62.0
2.0
61.5
1.0
61.0
60.5
2002
2003
2004
2005
Average Temp. (F)
64.9
64.5
62.2
63.3
Total Precip. (In.)
3.7
6.3
8.4
6.1
Year
0.0
Total Precipitation
)inches(
Average Temperature (degrees F)
Fort Collins Area Weather
(May through August Only)
Figure 3
Calls to CMC Office
City of Fort Collins Mosquito Program
Fish Request
1000
900
Bee/Moth Complaint
800
Allergy/Health
Complaint
Service Complaint
700
600
500
Request to Fog for
Special Event
Environmental Concern
400
300
200
100
0
Reporting Dead Bird
2003
2004
2005
Fish Request
0
0
2
Bee/Moth Complaint
0
0
1
Allergy/Health Complaint
0
0
1
Service Complaint
0
1
0
Request to Fog for Special Event
0
2
3
Environmental Concern
0
2
0
Reporting Dead Bird
1
20
2
Mosquito Annoyance
6
33
20
Misc.
10
53
13
Information Request
33
112
39
Reporting Standing Water
4
276
65
423
492
4
Add to Notification List (i.e., on website)
Mosquito Annoyance
Misc.
Information Request
Reporting Standing
Water
Add to Notification List
(i.e., on website)
Figure 4
Larvicide Products
Fort Collins Mosquito Program
1400
1200
1000
800
Acres Treated
One Helicopter
Treatment
Aug 19, 2003
600
400
200
0
2003
2004
2005
Temephos (conventional insecticide)
0
0.05
0
Methoprene (mosquito growth inhibitor)
0
154.2
32.8
Larviciding Oil
0
146.6
97.4
Bs (bacteria)
500
345.6
136.8
Bti (bacteria)
0
634.3
842.8
Year
Figure 5
Total Larval Sites per Year
City of Fort Collins
1,364
1400
# mosquito larval sites
1200
1000
867
800
600
400
70
200
0
2003
2004
2005
Figure 6
Adult Mosquito Population Trends
Fort Collins, CO
300
Avg. female mosquitoes per night per trap
280
260
240
243
220
200
180
160
140
120
100
80
60
63
40
43
20
0
2003
2004
2005
Figure 7
City of Fort Collins
Weekly Mosquito Population Trends
600
2003 (No mosq. control)
2004 (Full Larviciding Program)
2005 (Full Larviciding Program)
Avg. Females per night
500
400
300
200
178
104
100
115
116
86
52
14
15
27
17
26
56
71
44
37
33
28
5
6
3
0
May Wk. 2 Wk. 3 Wk. 4
Jun Wk. 2 Wk. 3 Wk. 4
Jul
Wk. 2 Wk. 3 Wk. 4 Wk. 5 Aug Wk. 2 Wk. 3 Wk. 4 Sept Wk. 2 Wk. 3 Wk. 4 Oct.
Wk. 1
Wk. 1
Wk. 1
Wk. 1
Wk. 1
Wk. 1
Date
Figure 8
Species Trends
City of Fort Collins
(CDC Light/CO2 traps)
Avg. # Female Mosq.per Trap Night
May 15 - Sept. 15
220
Misc. fem.
200
Anopheles hermsi
180
Cx Species
pipiens, Cx
160
restuans, Cx
140
salinarius, Cx
120
tarsalis, Cx
inornata,Cs
100
Ae/Oc Species
80
increpitus, Oc.
60
trivittatus, Oc
40
melanimon, Oc
dorsalis, Oc
20
vexans, Ae
0
2003
2004
2005
Figure 9
Fort Collins & Loveland
Culex tarsalis
300
Avg. Female Mosquitoes per trap per night
2003 FC Tarsalis
2003 LV Tarsalis
250
2004 FC Tarsalis
2004 LV Tarsalis
2005 FC Tarsalis
200
2005 LV Tarsalis
150
100
50
0
4/24-305/1-7 5/8-14 5/15-215/22-285/29-6/6/5-11 6/12-186/19-256/26-7/7/3-9 7/10-167/17-237/24-307/31-8/8/7-13 8/14-208/21-278/28-9/9/4-10 9/11-179/18-249/25-10
17
18
19
20
21
36
37
38
39
2003 FC Tarsalis
0.00
0.00
0.00
0.75
4.75
4.75 15.25 70.25 23.56 232.81 147.83 278.42 164.84 120.29 96.74 69.13 22.16 13.97 5.48
22
23
24
25
26
27
28
29
0.62
0.26
0.05
0.00
2003 LV Tarsalis
1.00
0.06
0.29
3.23
7.97
2.34
3.48
6.38 10.59 90.22 81.33 124.94 89.94 74.19 40.26 40.19 6.44
5.82
1.97
0.52
0.07
0.00
0.00
2004 FC Tarsalis
0.00
0.40
0.11
0.52
0.15
0.30
0.93
0.93
0.59
2.37
5.76 15.26 14.00 11.74 19.91 13.35 16.24 3.34
2.74
1.31
0.46
0.06
0.17
2004 LV Tarsalis
2.00
0.73
0.67
0.45
0.23
0.50
1.06
0.32
1.50
1.79
3.38 16.46 8.71
2.53
1.16
0.23
0.08
0.09
2005 FC Tarsalis
0.00
0.00
0.00
2.00
1.95
0.67
1.00
1.87
4.80
7.61 27.65 58.02 58.48 30.31 22.39 20.78 18.43 12.28 7.03
5.44
0.50
0.26
0.00
2005 LV Tarsalis
0
0.00
0.00
2.00
2.19
0.95
0.85
2.40 16.08 17.14 25.03 54.62 76.71 35.17 23.49 27.75 21.64 11.36 6.58
4.62
2.39
0.50
0.11
Week/Date
30
31
32
33
34
8.54 14.06 20.59 17.85 5.68
35
Figure 10
Fort Collins
Culex pipiens
35
2003 FC Pipiens
Avg. Female Mosquitoes per trap per night
30
2004 FC Pipiens
2005 FC Pipiens
25
20
15
10
5
0
4/24-30 5/1-7
5/8-14
5/15-21 5/22-28 5/29-6/4 6/5-11
6/12-18 6/19-25 6/26-7/2 7/3-9
7/10-16 7/17-23 7/24-30 7/31-8/6 8/7-13
8/14-20 8/21-27 8/28-9/3 9/4-10
9/11-17 9/18-24 9/25-10/
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
2003 FC Pipiens
0.00
0.00
0.00
0.00
0.25
0.00
0.00
0.50
0.00
9.75
28.60
28.97
15.23
30.19
20.39
13.72
16.69
9.78
3.70
0.62
0.52
0.48
0.14
2004 FC Pipiens
0.00
0.10
0.00
0.05
0.03
0.58
0.51
0.68
0.37
1.02
2.98
3.49
6.61
7.16
6.67
3.74
5.71
1.85
2.52
1.59
1.25
0.00
0.25
2005 FC Pipiens
0.00
0.00
0.00
0.11
0.05
0.17
0.04
0.47
0.67
0.91
3.72
3.36
3.28
4.17
4.68
6.04
6.50
7.03
4.60
4.76
1.55
1.43
1.61
Week/Date
Figure 11
Fort Collins
Floodwater (i.e., Nuisance) Mosquitoes
Avg. Female Mosquitoes per trap per night
300
2003 FC Floodwater
2004 FC Floodwater
2005 FC Floodwater
250
200
150
100
50
0
4/24-35/1-7 5/8-145/15-25/22-25/29-66/5-116/12-16/19-26/26-77/3-9 7/10-17/17-27/24-37/31-88/7-138/14-28/21-28/28-99/4-109/11-19/18-29/25-1
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
2003 FC Floodwater 0.00 1.00 10.67 2.50 30.75 3.50 13.50 107.5 39.11 144.6 71.13 163.2 39.52 39.42 77.90 52.66 29.69 11.91 8.63 4.97 27.48 3.33 0.52
2004 FC Floodwater 0.21 6.60 0.78 1.86 2.98 47.83 27.59 27.90 15.44 26.90 68.83 79.72 25.07 14.67 38.21 13.65 11.18 40.51 10.89 18.34 6.46 0.69 1.50
2005 FC Floodwater 0.00 0.00 0.00 10.78 11.10 13.21 11.87 19.64 132.5 90.11 48.24 43.87 47.48 14.48 29.91 40.22 18.68 15.97 18.87 15.32 2.41 3.26 0.61
Week/Date
COLORADO MOSQUITO CONTROL, INC.
Protecting Colorado From Annoyance & Disease Since 1986